A report by the House of Commons Public Affairs found that thousands of BBC employees, including many household names, were being paid via private companies, meaning the Corporation was not liable for their national insurance payments.

David Smith, head of employee tax at the BBC, admitted that 25,000 contracts covering around 1,500 workers had been issued on a freelance, off-books basis, but insisted the Corporation abided by the rules.

He conceded, however, that the use of so-called service companies, particularly by on-air "talent," allowed the BBC to "cut [its] exposure" in cases where the HMRC ruled that the person involved was not a genuine freelancer.

"The reason behind this is just in case HMRC were to disagree that the person was not a freelancer ... and protects the licence fee from any further exposure," he said.

Mr Smith was questioned about the BBC's tax arrangements by John Humphrys, the long-running presenter of BBC Radio 4's Today Programme, who disclosed that he himself was a freelancer, although he does not have a service company .

Saying that most of the 1,500 people paid through the use of such companies were "off-air" workers, such as makeup artists and cameramen, who worked on a sporadic basis, he added that most actors and musicians were accustomed to being paid as freelancers.

In their report, the MPs highlighted the use of service companies by long-serving presenters such as Jeremy Paxman and Anne Robinson.

By using a service company, individuals can minimise their liability for national insurance by paying themselves dividends rather than a salary.

Mr Smith denied that the BBC encouraged its stars to be paid in this way, and said that the scheme was designed to be "tax neutral" because the individuals themselves were supposed pay national insurance.

He said it was up to the presenters to prove to the HMRC that they were "genuine freelancers" and insisted that the BBC abided by the law at all times.

The BBC has said that it will investigate the use of service companies by on-air talent.

On the same programme, John Whiting, of the Office for Tax Simplification, said the Inland Revenue had not been applying its anti-avoidance provisions as diligently as it should have.

He went on: "If you are just an ordinary freelancer, which is a pretty ordinary situation these days ... it’s a personally sensible way of organising your affairs. It makes every sort of sense.

"What this report is focusing on, looking at and targeting, is people who are often in what’s often called disguised employment – they’re really an employee but they’re putting the aura around them that they’re operating as a company.

“The point is, if you’re in that situation, the tax man does have an anti-avoidance provision, a very notorious one, generally known as IR35.... If that operates properly then someone who is in disguised employment, if you really just take away this flim-flam of the company, they’d be an employee. Then they’d have to operate PAYE, National Insurance, through their company.

"One of the things this report points out is that provision isn’t difficult to point out, the Revenue haven’t been applying it in perhaps as many situation as they should and therefore in the parlance, the fear is, people have been ‘getting away with it’.”